Medical implant and method of implantation

ABSTRACT

A medical implant and a method of implanting a medical implant are disclosed. The medical implant ( 20 ) is elongate and for fixation in a patient, and comprises an apical bone anchoring portion ( 200 ) for bone apposition, and an unthreaded coronal portion ( 210 ), wherein said coronal portion ( 210 ) has a length (L 2 ) exceeding or equaling a length (L 1 ) of said apical portion ( 200 ), and wherein said apical portion ( 200 ) has a maximum outer diameter (D 1 ) that is equal to or larger than a maximum outer diameter (D 2 ) of said coronal portion. In a method of implanting a medical implant, an apical part is affixed in the zygomatic bone, and a coronal part is positioned outside the maxilla in the mucous membrane.

PRIORITY INFORMATION

This application is a continuation of U.S. patent application Ser. No.13/003,260, filed Mar. 31, 2011, which is the 371 National Phase ofPCT/EP2008/005585, filed Jul. 9, 2008, the entirety of which is herebyincorporated by reference herein.

FIELD OF THE INVENTION

This invention pertains in general to the field of medical implants andmethods for implantation of such implants. In particular, the inventionrelates to dental implants and methods for their implantation.

BACKGROUND OF THE INVENTION

Various types of medical implants are known, e.g. as anchoring elementsthat are intended to be implanted in patients' jaws. Upon implantationthese anchoring elements support e.g. dental restorations via aconnection interface.

Due to various reasons, such as diseases, bone quality may be poor incertain bone regions of a patient. In edentulous or partly edentulouspatients jaw bone tissue may be highly resorbed. Therefore it may bedifficult or impossible to satisfactorily anchor conventional medicalimplants in such damaged or resorbed bone tissue regions. For instancein the maxilla, i.e. the upper jaw, special elongate anchoring elementsmay be used that are anchored both in the maxilla and in the oszygomaticus, i.e. the zygomatic bone. Conventionally, the anchoringelement is affixable by a double anchoring technique in the maxilla andthe zygomatic bone. Between the maxilla and the zygomatic bone theanchoring elements extend through a cavity in the skull, the maxillarysinus cavity.

In U.S. Pat. No. 5,362,236 and U.S. Pat. No. 5,564,926 such an elongateanchoring element and a method of implanting the anchoring element aredisclosed. The anchoring element has two generally cylindrical portionswith different diameters. A threaded apical end portion of the anchoringelement has the smaller diameter thereof, and is intended to bepositioned in the zygomatic bone. A threaded coronal portion of theanchoring element has the larger diameter thereof, and is intended to bepositioned in the maxilla. The anchoring element is implanted bydrilling two aligned bores in the bone tissue. The apical, smallerdiameter, portion of the anchoring element is passed through the largerdiameter bore in the maxilla and is threaded into the smaller diameterbore in the zygomatic bone. While self-threading by the apical, smallerdiameter, portion takes place in the second bore, the larger diameterportion is self-threaded in the first, larger diameter, bore in themaxilla. Thus, the anchoring element may be reliably double anchoredwhen applied.

However, both anchoring elements and methods, such as disclosed in U.S.Pat. No. 5,362,236 and U.S. Pat. No. 5,564,926 may be further improvedor provided with alternatives. An alternative anchoring element isdisclosed in WO2005/079697. The anchoring element comprises a firstfixation portion, disposed at the apex, a second fixation portion,disposed at the basis of the anchoring element, and an intermediateportion in between the first and second fixation portion.

For instance, working inside and from inside the maxillary sinus may bedifficult due to limited visibility, space etc. Access hole in themaxillary bone is sometimes opened towards the maxillary sinus cavity,in order to gain a field of sight into the maxillary sinus cavity.However, this may be both cumbersome and imply healing complications forthe patient.

Thus, there is a need for an improved medical implant and/or medicalmethod for implanting a medical implant. Hence, an improved medicalimplant and/or medical method for implanting a medical implant would beadvantageous. In particular a medical implant and/or medical method forimplanting a medical implant allowing reliable anchoring in bone tissue;increased surgical flexibility; improved surgical control, e.g. byimproved visible feedback of the medical procedure; and/orcost-effectiveness, e.g. by reduced surgery time, patient recovery time,potential side effects; etc. would be advantageous.

SUMMARY OF THE INVENTION

Accordingly, embodiments of the present invention preferably seek tomitigate, alleviate or eliminate one or more deficiencies, disadvantagesor issues in the art, such as the above-identified, singly or in anycombination by providing a medical implant and a method of implanting amedical implant according to the appended patent claims.

According to one aspect of the invention, a medical implant is provided.The medical implant is an elongate medical implant for fixation in apatient. The implant comprises an apical bone anchoring portion for boneapposition, and a non-threaded coronal portion, wherein the coronalportion has a length exceeding a length of the apical portion, andwherein the apical portion has a maximum outer diameter that is equal toor larger than a maximum outer diameter of the coronal portion.

According to another aspect of the invention, a method of implanting amedical implant in a patient in a medical procedure is provided. Themethod comprises creating a first recess in a facial surface of bonetissue of a maxilla of the patient; creating an anchoring boreexternally in facial skull bone tissue at a distance from a location ofthe first recess in the facial surface of the maxilla; and implanting amedical implant with an apical anchoring portion thereof in theanchoring bore, and positioning a non-threaded coronal part of themedical implant adjacent the first recess.

The medical implant and the method enables a more beneficial positionand location of the implant interface against the bridge or tooth/teethreplacement. This in turn provides for use of a less voluminousreplacement. Furthermore, the implant describes an alternative path fromthe zygomatic bone, which does not occupy so much space in the oralcavity. This is considered advantageous for esthetic reasons andprovides for more space for the tongue. The beneficial position of theinventive implant, when attached to the zygomatic bone in accordancewith the method, in relation to the dental restoration allows for a morealigned load transfer, which may alleviate the surrounding body parts aswell. Further embodiments of the invention are defined in the dependentclaims, wherein features for the second and subsequent aspects of theinvention are as for the first aspect mutatis mutandis.

Some embodiments of the invention provide for a fixture of a dentalrestoration that provides for improved anchoring.

Some embodiments of the invention also provide for an improved medicalimplant that provides reliable anchoring in skull bone tissue and aconnection interface at an alveolar ridge of a maxilla.

Some embodiments of the invention provide for a medical implant thatfacilitates implantation thereof.

Some embodiments of the invention provide for a method of implanting amedical implant, wherein visibility of the implantation is improved.

Thus, some embodiments provide for improved precision and safety ofimplantation.

Some embodiments provide for a medical procedure of implanting a medicalimplant that is more securely and less complicated to perform for asurgeon. Some embodiments provide for increased surgical flexibility.Some embodiments provide for improved surgical control, e.g. by improvedvisible feedback of the medical procedure. Some embodiments provide forcost-effectiveness, e.g. by reduced surgery time, patient recovery time,potential side effects, etc.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of which embodiments ofthe invention are capable of will be apparent and elucidated from thefollowing description of embodiments of the present invention, referencebeing made to the accompanying drawings, in which

FIGS. 1A and 1B are perspective views of prior art medical implants;

FIGS. 2A, 2B, and 2C are a perspective view and a lateral view of anembodiment of a medical implant and a coronal end portion thereof incross section;

FIGS. 3A, 3B, and 3C are similar FIGS. 2A-2C illustrating anotherembodiment of a medical implant;

FIGS. 4A, 4B, and 4C are views illustrating a conventional medicalimplantation procedure via the sinus cavity;

FIGS. 5A and 5B are a frontal view and a lateral view illustratingimplanting of a medical implant; and

FIG. 6 is a flow chart illustrating a medical procedure of anembodiment.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the invention will now be described withreference to the accompanying drawings. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art. Theterminology used in the detailed description of the embodimentsillustrated in the accompanying drawings is not intended to be limitingof the invention. In the drawings, like numbers refer to like elements.

The following description focuses on an embodiment of the presentinvention applicable to a dental implant for anchoring in skull bone,such as the zygomatic bone. Such anchoring dental implants are alsoreferred to as fixtures. However, it will be appreciated that theinvention is not limited to this application.

The medical implants 100, 101 shown in FIG. 1A and FIG. 1B comprise twolongitudinally adjoining cylinder-shaped segments. FIG. 1A correspondsto FIG. 1 of U.S. Pat. No. 5,362,236 and U.S. Pat. No. 5,564,926 of thesame proprietor as the applicant of the present application, whichhereby are incorporated in their entirety for all purposes. The implantis essentially composed of two cylindrical segments bordering each otherand being in alignment, wherein the first, coronal segment 1 has adiameter larger than that of the second, apical segment 2.

The outside of the implant is threaded, except for a mounting portionextending from the coronal end of the implant and connected to thecylindrical coronal segment 1. The outer threads comprise first threads4 on the coronal cylindrical segment 1 and second threads 5 on theapical cylindrical segment 2. The pitch is the same for both threads 4,5 merging at the border zone between the cylindrical segments. The innerdiameter of first threads 4 is larger than the outer diameter of thesecond threads 5. Threads 4, 5 are self-tapping.

A symmetrically centered bore 17 extends from the apical end 6 and hasan extension corresponding to about half the length of the apicalsegment 2. Two through slits 7, 8 arranged symmetrically in segment 2and in its longitudinal direction extend from a plane perpendicular tothe central axis near the apical end 6. Slits 7, 8 establishcommunication between the outside of apical segment 2 and thesymmetrically centered bore 17 arranged therein for transport of bonematerial removed by ablation. The outside of apical segment 2 is beveled(beveling 16) towards apical end 6.

The mounting section 3 is contained within a cylindrical chamber with adiameter corresponding to the outer diameter of coronal cylindricalsegment 1. The mounting segment 3 comprises a base portion 9 having theform of a cylindrical body dissected by a plane at an angle of 45 DEG inrespect of the cylinder axis. The circular basis of base portion 9 isconnected to the coronal end of the coronal cylindrical segment 1 withwhich it merges. Nearest to the coronal cylindrical segment 1 baseportion 9 has an annular flange 14 to which an annular groove 15connects in direction of the coronal end. End face 10 of base portion 9is defined by a dissecting plane and, at its coronal zone, smoothlyrounded joins the cylinder mantle of base section 9, the beadingdecreasing gradually towards the apical portion of the base section.Because of the beveling the profile of end face 10 is substantiallycircular. In its center end face 10 has a bore 12 running at an angle of45 degrees in respect of longitudinal axis A of the implant 100. At bore12 base section 9 is extended under formation of a frustum of a cone 11tapering in direction away from base section 9. Mantle surface 13 of thecone frustum 11 and the annular end face 10 are designed for sealingabutment of a dental prosthesis or bridge (not shown) that can bemounted on the base portion by screw means.

The implant 101 shown in FIG. 1B differs from the implant 100 of FIG. 1Ain that the connection interface comprises a hexagonal unit 111 insteadof the frusto conical part 11.

FIGS. 2A and 2B illustrate embodiments of an elongate medical implant20. The elongate medical implant 20 is devised for fixation in bonetissue in a patient.

The implant 20 comprises a helically threaded apical bone anchoringportion 200 for bone apposition. A tapered top portion 201 is providedat the apical portion 200. The top portion is tapered towards an apicalend of the implant 20. The tapered top portion 201 of the implant 20 istapered with a tapering angle in the range between 25 to 75 degrees.Thanks to the tapered top portion, entry into a bore is readily foundupon implantation. The implant 20 is homing and self-centering in thebore. This is particularly advantageous, when the bore is partly hiddenor obscured. Thus, the tapered top portion 201 facilitates insertion ofthe apical end of implant 20 into a bore.

The apical portion 200 may be cylindrical except for the tapered topportion 201. The apical portion 200 may also be slightly taperingtowards the top portion 201 for improved primary stability of theimplant upon implantation.

A diameter of the apical end by the tapered top portion 201 is less thanhalf of the maximum outer diameter of the apical portion (D1).

Alternatively, the apical portion 200 may be conical or at least partlyconical, tapering towards the tapered portion 201. Tapered portion 201may in some embodiments comprise a bevel at the apical end.

The thread of the helically threaded apical bone anchoring portion 201is, upon implantation in bone tissue, used to convert between rotationaland linear movement. That means by rotating the implant 20 the implant20 is screwed into the bore in longitudinal direction thereof. The peakand valley structure of the thread provides a primary stability of theimplant 20 in the bone tissue.

In other embodiments the implant may alternatively, or in addition,comprise other bone anchoring structures than a helical thread. Theapical portion may be provided with other bone engagement interfaces.The apical portion may for instance be devised to provide fixation byfrictional engagement in the bore. Fixation of the apical portion tobone tissue may also be provided by structures providing pressuretowards the appositioned bone tissue, similar like a plug or peg. Suchstructures may be annular ribs. A trade off between implantation timeand primary stability, as well as long-term osseointegration of theimplant may be made.

The implant 20 further comprises an unthreaded coronal portion 210.Unthreaded means that no thread is present along the coronal portion210. An alternative term to unthreaded in this context is non-threaded,i.e. there is no peak and valley structure of a thread provided at thecoronal portion 210. The coronal portion 210 is substantially smooth ona macro level. The macro roughness (explained below) of the coronalportion 210 is substantially lower than that of the anchoring portion.

This provides for a portion of the implant 20 that is arranged to notirritate or damage appositioned soft tissue, such as gingiva, includingembedded muscles, blood vessels, or nerves. However, the surface of thenon-threaded coronal portion may be provided with a surface roughness ona micro level, as is elucidated below.

In other embodiments the term unthreaded comprises that thesubstantially smooth extension of the coronal portion 210 is free ofbone anchoring structures. The coronal portion 210 is free ofprojections that may affect appositioned soft tissue.

Conventional anchoring elements, such as disclosed in U.S. Pat. No.5,362,236 and U.S. Pat. No. 5,564,926, may comprise threaded portionsthat are appositioned to tissue when applied. However, threaded portionsof the anchoring element may irritate or damage the tissue, e.g. in themaxillary sinus cavity. Also, tissue from the maxillary sinus may becaught by the thread of the apical part of the anchoring element, whichmight lead to impaired osseointegration and secondary stability in thezygomatic bone and eventually loosening of the anchored implant.

Embodiments of the invention provide for improved soft tissueapposition. Thanks to the unthreaded portion 210, a normal physiologicalfunction of the soft tissue is provided when appositioned to the implantat that portion of the dental implant. Conditions, such as soft tissueirritation or damage, catarrh or irritation of the mucous membrane areeffectively prevented. A prophylactic treatment is comprised in thisprevention.

The coronal portion 210 may have a surface with a coarse microroughness, wherein the coronal portion 210 is adapted to provide atissue friendly portion.

The outer surface of the implant 20, hereinafter also called “surface”for the sake of simplicity, may have a topography with a macroroughness, e.g. in the form of one or several threads at the anchoringportion 200 in order to mechanically anchor the medical implant insurrounding bone tissue. Topography is amongst others defined as thestudy or detailed description of the surface features of a region of anobject, here of the medical implant. The medical implant has an outersurface and the geometry thereof follows a defined topography both on amacro scale and a micro scale.

The macro roughness defines the outer geometry of the medical implant.In FIGS. 2A and 3A, the macro roughness is illustrated in the form of athreaded part of the medical implant 20 or 30. Additionally, the macroroughness of the threaded outer surface 40 may in itself have a surfaceroughness, for instance defined as a porosity of the surface, but thisis referred to below as micro roughness. The macro roughness of thesurface lies for instance for a medical implant in the mm range, whereinthe macro roughness may further be subdivided into finer structures,such as grooves on threaded portions, or non-threaded portions in thesub mm range.

Furthermore, the outer surface of the medical implant may have a microroughness in the μm range. The micro roughness defines the topography ofthe surface of embodiments of medical implants in the present context.In contrast, the above-described macro roughness is defined by the outercontour of the medical implant.

For instance, in case the implant 20 is a ceramic implant, the outersurface topography may be machined and densely sintered without aprocessed outer surface thereof, i.e. after sintering the ceramicmedical implant, has a very fine micro roughness. Coronal portion 210may advantageously have such a surface. However, such a smooth outersurface has disadvantageous properties with regard to osseointegrationof the medical implant. Therefore, the anchoring portion may be providedwith a more coarse or rough outer surface having an increased microroughness compared to the untreated sintered outer surface, whichimproves osseointegration thereof. Such a coarse or rough outer surfacemay for instance be provided in the form of a porous, rough surfacelayer, having an outer surface roughness, for instance with a Ra value(explained below) in the μm range. For example, in WO 2005/027771, ofthe same applicant as the present application, which is incorporatedherein by reference in its entirety, discloses a densely sinteredceramic medical implant having a ceramic layer arranged thereon. Theceramic layer, and thus an outer surface of the dental implant, isprovided with a surface that has a porosity, which is larger or has morepores than in the underlying densely sintered ceramic material. In thismanner, a ceramic medical implant is provided that fulfills therequirement of mechanical strength, and a considerable improvement ofosseointegration is achieved. At the same time advantageous propertiesare achieved at the portion having a fine micro roughness at the coronalportion 210. Alternatively, the outer micro roughness of a ceramicmedical implant may be provided on a ceramic substrate thereof bymodifying the sintered outer surface, e.g. by chemical or mechanicalabrasion methods, as for instance disclosed in US-A1-2005/0106534.

The medical implant 20 may be manufactured of other biocompatiblematerials, such as titanium oxide. In this case, the implant may beprovided with a desired surface roughness. For instance the TiUnite®surface may be provided, as disclosed in WO0174412 or WO03003936 of sameapplicant as the present application, which are hereby incorporated intheir entirety by reference for all purposes. The TiUnite® surface has arelatively high surface roughness and porosity.

Medical implants having such a suitable surface roughness reachimmediately upon implantation a primary stability in bone tissue by themacro roughness, i.e. the macro structure of e.g. threads of theimplant. The medical implant then osseointegrates with the surroundingbone tissue within a healing time of about 3 to 4 months, so that asecondary stability is provided, i.e. a permanent bond between thethreaded anchoring part 200 of the medical implant screwed into the bonetissue and the bone tissue is provided. However during a certain timefollowing the implantation, the total stability of the medical implantin the bone tissue decreases to a certain stability that is lower thanthe initial stability, i.e. the stability of the medical implant shows astability dip after implantation. Then bone growth accelerates andosseointegration is achieved. Pores of the rough surface, into which thebone tissue is growing firmly, provide the secondary stability. Inaddition, also a mucous membrane may advantageously be in apposition toa surface having a coarse micro roughness, but a fine macro roughness.

A measure for surface roughness is parameters, such as Ra value (meanroughness), Rt value (maximum roughness), Sa value etc. The mean oraverage roughness (Ra) is defined as the average of absolute distancevalues of a number of measurements across a surface of interest. Sa isthe equivalent amplitude parameter on a 3D or areal basis.

Roughness measurements may for instance be performed according toprocedures as determined in international standards. However,measurements in accordance with such international ISO standards mayprove difficult to implement on dental implants, e.g. due to the smallsurfaces thereof.

Attempts have been made to define and measure surface roughness of priorart dental abutment and dental implants (see e.g., Wennerberg, Ann etal., Design and Surface Characteristics of 13 Commercially AvailableOral Implant Systems, JOMI, Vol. 8, No. 6 pages 622-633, (1993), whichhereby is incorporated by reference in its entirety). The Wennerbergarticle defines two surface roughness parameters: (i) Rt, which is themaximum peak to valley height of the profile of the surface (see page623) and (ii) Ra, which is the mean value of the peak to valleydistance.

Using the Wennerberg definitions, smooth machined and/or polishedsurface of implants have a Rt of approximately 10 microns or less and aRa of approximately 0.6 microns or less.

The coronal portion 210 has a length L₂ exceeding a length L₁ of theapical portion 200. The apical portion 200 has a maximum outer diameterD₁ that is larger than a maximum outer diameter D₂ of the coronalportion 210. In a specific embodiment D₁ is equal to D₂.

The apical bone-anchoring portion 200 is devised for apposition to azygomatic bone of the patient, as will be illustrated below.

The coronal portion 210 is at least partly devised for apposition tosoft tissue, including gingiva and muscle tissue, of the cheek exteriorof the maxilla. In an embodiment the coronal portion 210 is cylindricalalong its entire length.

The coronal portion 210 may be devised for partial apposition to bonetissue and partial apposition to non-bone tissue. For instance theradial portion of the coronal portion oriented towards the maxilla uponimplantation may be appositioned to the maxilla. As the implant 20 willbe positioned outside of the maxilla, the outer radial part of thecoronal portion 210 oriented away from the maxilla, towards the softtissue may be devised for radial apposition to this soft tissue.

In embodiments the coronal portion 210 has a diameter D₂ that is smallerthan an inner diameter of a thread of the apical portion 200 at themaximum outer diameter thereof, D₁.

As D₂ is smaller than D₁, a plurality of implants may be positioned withtheir coronal ends close to each other. Thus, stability of a dentalrestoration may be improved in that a plurality of implants fits in thenarrow space at hand for this.

In embodiments, the coronal portion may be rotationally asymmetrical(not shown). This provides for improved anatomical flexibility whenpositioning the implant.

In practical embodiments the dental implant, as shown in FIGS. 2A-2C and3A-3C may have the following approximate ranges and/or values of lengthand diameter thereof:

Total length (L₁+L₂): 30 mm to 55 mm

L₁ typically 15 mm

L₂: 15 to 40 mm

Ratio (L₁/(L₁+L₂)): approx 0.25 to 0.50

Ratio (L₁/L₂)): approx 0.35 to 1.0

D₂: is typically smaller than the diameter of the valleys of the threadsor other grooves at the apical portion 200

Ratio (D₁/D₂)): 0.5 to 0.95

In embodiments, a ratio of the length of the apical portion (L1) to thelength of the coronal portion (L2) is in the range of 0.2 to 0.5.

The total length of the implant is the length of the apical portion plusthe length of the coronal portion thereof. Any except further portions,e.g. protruding from the coronal portion are not included in the totallength. Further protruding portions may for instance be mountingportions extending from a coronal end of the implant.

Conventionally, anchoring elements, such as disclosed in U.S. Pat. No.5,362,236 and U.S. Pat. No. 5,564,926, have a bore having internalthreads formed about an axis that is tilted with respect to a commonaxis for the cylindrical segments. External threads on prosthesisthreadably engage the internal threads to secure such prosthesis to theanchoring element. However, due to the tilting angle, the mountingprocess may be cumbersome.

Traditionally, the conventional zygoma implants have their coronal endpositioned at a distance from the alveolar ridge in a palatal direction,i.e. towards the inside of the oral cavity, such as shown in FIG. 4 a,4B or 4C. Thus, it may be difficult to provide a dental restoration atan anatomically correct position, as a distance from the coronal end ofthe zygoma implant to the position of the original alveolar ridge of themaxilla has to be bridged.

However, according to embodiments of the invention, these issues aresolved. A connection interface of a medical implant may be providedclose to or at the alveolar ridge of the maxilla.

In more detail, the implant 20 moreover comprises a connection interface220 for attachment of an abutment and/or a dental restoration, such as atooth prosthesis or a bridge.

The connection interface 220 may comprise an inner helical thread at thecoronal end of the implant 20 that is arranged substantially indirection of the longitudinal direction of the medical implant

Conventional implants, such as shown in FIGS. 1A and 1B have a bore 12running at an angle of e.g. 45 degrees in respect of longitudinal axisof the implant 100. The bore 12 defines the orientation of a connectioninterface for receiving an abutment carrying a dental restoration. Theorientation of the bore 12, due to the angular orientation, is dependenton the rotational position of the implant upon implantation. Therefore,care has to be taken that the implant is screwed into a defined positiontowards an ideal occlusion plane.

As shown in FIG. 2C, the threaded internal bore 221 of the connectioninterface 220 of the embodiment is oriented substantially in line withthe longitudinal axis of implant 20. Thus an abutment connectioninterface is arranged substantially perpendicular to a longitudinaldirection of the medical implant 20. Mounting of an abutment is thusadvantageously facilitated, irrespectively of the rotational orientationof the implant upon implantation. The abutment may have a secondconnection interface that is angled in relation to the longitudinal axisof the implant 20, e.g. for attachment of a bridge, tooth prosthesis orsimilar dental restoration.

The implant 20 may be produced in a single monolithic piece. The implant20 may alternatively be split in at least two interconnectable parts.For instance a connection interface may be provided between the apicaland the coronal portion.

An application of implants 20, 30 will now be described with referenceto a surgical method.

FIGS. 4A, 4B, and 4C are views illustrating a conventional medicalprocedure for implantation of a medical implant by double anchoring viathe sinus cavity. Anchoring elements, such as described above withreference to FIG. 1A and FIG. 1B, have two portions with differentdiameters. The threaded apical end portion 2′ of the anchoring element1′ has the smaller diameter thereof, and is intended to be positionedinteriorly in the zygomatic bone Z. The threaded coronal portion 4′ ofthe anchoring element 1′ has the larger diameter thereof, and isintended to be positioned in the palatal region of the maxilla M. Theanchoring element 1′ is implanted by drilling two aligned bores in thebone tissues. A first bore, having a diameter suitable for anchoring thecoronal portion, is drilled through the maxilla M. Drilling is continuedthrough the maxillary sinus cavity 17 in the skull. Subsequently asecond bore 5′, having an appropriate diameter for anchoring the apicalportion of the anchoring element, is drilled in the zygomatic bone Zfrom inside the maxillary sinus 17. The apical, smaller diameter,portion of the anchoring element is passed into the bore in the maxillaM and is threaded into the bore in the zygomatic bone Z. Whileself-threading by the apical, smaller diameter, portion takes place inthe second bore, the larger diameter portion is self-threaded in thefirst bore in the maxilla. Thus, the anchoring element is doubleanchored. In FIG. 4B a dental bridge 410 is shown affixed to a pluralityof implants 101 and 400, 401, 402, 403.

However, this conventional method has some drawbacks, as describedabove. In contrast to this conventional method, an improved method isprovided. In an embodiment of the method, a first recess is made in theexterior bone surface of the maxilla, which is oriented towards thefacial side of the maxilla, i.e. outside of the oral cavity. Removingbone tissue from the maxilla surgically creates the first recess. Thefirst recess is made to provide a passage for the coronal portion of ananchoring element on the outside of the maxilla towards the alveolarcrest thereof. The first recess does usually not extend into themaxillary sinus cavity and a remaining amount of bone tissue underlyingthe first recess is kept. The first recess commonly has a longitudinalextension oriented towards the exterior of a bone tissue at thezygomatic bone located on the same side of the skull as the firstrecess. Along its longitudinal extension, the first recess may beprovided as a guide channel for a tool when creating an anchoring boreat the zygomatic bone. For instance a drill may be guided by the firstrecess towards an entry site of the anchoring bore when drilling a borein the zygomatic bone. Thus, the longitudinal extension of the firstrecess in the outer surface of the maxilla is aligned with thelongitudinal extension of the anchoring bore in the zygomatic bone.Creating the anchoring bore, such as by a drilling operation inaccordance with the invention, may be made under good visibility of thesurgical working area. Subsequent implantation of a medical implant inthe anchoring bore is made. The medical implant, when thus applied,extends from its apical end in the anchoring bore to its coronal portionat the first recess towards the alveolar crest of the maxilla.

Further embodiments of this method of implanting a medical implant in apatient will now be described. A specific embodiment will be elucidatedfurther below with reference to FIGS. 5A, 5B and FIG. 6. FIG. 5A is afrontal view illustrating a medical implant 20 implanted extramaxillary. FIG. 5B is a lateral view illustrating the same situation. Inaddition, a conventional implant 101 is indicated, purely forillustrative purposes, in order to illustrate the difference between thepresent extra maxillary method and the conventional maxillary sinuscavity crossing method. For illustrative purposes the conventionalimplant is disclosed as attached for interconnecting with a bridge orsimilar at substantially the same location in the mouth as the inventiveimplant. This illustration discloses that the apical portions in suchhypothetical case, end up at a very different locations. Since, the bonequality of the anchoring bone is decisive for how and where the implantcan be affixed it would probably have been more correct to illustratethe different resulting positions of the coronal end portion of therespective implants instead. However, this situation is not illustratedand needs to be imagined. It is not considered difficult to understand,with hindsight, that there is a risk for the implant of the conventionaltype and hence applied by conventional methods to occupy more space bythe palate cavity than is needed by shifting to the herein claimedtechnique.

In the present medical procedure, a medical implant is implanted in apatient. The medical procedure comprises creating a first recess in afacial surface of bone tissue of a maxilla of the patient; creating ananchoring bore externally in facial skull bone tissue at a distance froma location of the first recess in the facial surface of the maxilla; andimplanting a medical implant with an apical anchoring portion thereof inthe anchoring bore, and positioning a non-threaded coronal part of themedical implant adjacent the first recess.

The skull is normally made up of a number of skull bones. For instancethe adult human skull comprises twenty-two bones. Except for themandible, i.e. the lower jaw, all of the skull bones are joined togetherby sutures, semi-rigid articulations formed by bony ossification,whereby the presence of Sharpey's fibres permits a little flexibilitybetween the skull bones.

In embodiments of the method, the facial skull bone tissue is comprisedin the zygomatic process at the zygomatic bone. The zygomatic process isa protrusion from the rest of the skull. Most of it belongs to thezygomatic bone, but there are other bones contributing to it too, namelythe frontal bone, maxilla and temporal bone.

When creating the anchoring bore, caution has to be made not to injureany anatomical sensitive structures, like nerves or vessels, e.g.passing through foramen in the maxilla or zygomatic bone.

The method may comprise embedding the coronal part of the medicalimplant under gingival tissue, once the anchoring in the anchoring boreis made. The method may comprise embedding the coronal part of themedical implant between the gingival tissue and the first recess. A flapof gingival tissue may be put back to its original position for thispurpose and sutured for healing.

The method may comprise creating the first recess with a longitudinalextension, and wherein the creating the anchoring bore comprisescreating the anchoring bore substantially in line with the longitudinalextension of the first recess. In an embodiment creating the anchoringbore is made by drilling a cylindrical bore with a bore diameter, borelength, and bore longitudinal orientation.

Preferably, the bore diameter is made in a dimension between that of thediameter of the apical end portion and the diameter of the apical(threaded portion) portion itself. The threads of the tapered apicalportion may initially be easily introduced into the anchoring bore ofthe bone. The anchoring stability is then assured in accordance with apreferred method due to the larger diameter of the apical portion inrelation to that of the bore when the implant is further introduced. Thehelical threads starting from the tapered portion thereof will assureduring introduction of the implant in the bore that the implant may betapped further down the hole. The tapering angle is defined in thedrawings with the symbol a and is between 25 and 70 degrees.

Creating the first recess may in an embodiment be creating anindentation in the facial surface of the maxilla having a longitudinalextension, a maximum depth, and a maximum width. The maximum width isequal to or less than the bore diameter. The skull bone is in anembodiment the maxilla at a facial side of the skull of the patient atthe indentation, and wherein the drilling a cylindrical bore is drillingthe cylindrical bore in the maxilla at a zygomatic process, wherein thedrilling the bore is made substantially aligned with the longitudinalextension of the indentation.

The anchoring may be made with an apical part of a medical implanthaving a larger diameter than the coronal portion thereof. Thus reliableanchoring is provided in a large anchoring bore. At the same time, anarrower coronal portion provides for several advantages. The firstrecess needs not be as large, i.e. the amount of bone tissue removed islimited. This is both patient friendly, and leaves sufficient remainingbone tissue of the maxilla such that mechanical strength thereof is notthreatened. In addition, as the coronal portion takes less volume,potential irritation of surrounding tissue is minimized. Moreover, it isfacilitated to implant a plurality of such medical implants in thenarrow space available. Mechanical stability of the dental implant andprecision of dental restorations attached thereto are maintained.

In an embodiment the skull bone is a zygomatic bone of a facial side ofthe skull of the patient at the indentation, and wherein the drilling acylindrical bore is drilling the cylindrical bore in the zygomatic bone,wherein the drilling the bore is made substantially aligned with thelongitudinal extension of the indentation. The first recess may be usedas a guide channel for a drill when drilling the bore in the zygomaticbone, whereby the first recess in the outer surface of the maxilla isaligned with the bore in the zygomatic bone.

The method may further comprise using the first recess as a guidechannel for a tool creating the anchoring bore, whereby aligning theanchoring bore with the first recess is provided. The anchoring bore maybe s created along a line of sight from the first recess. Creating theanchoring bore may be made under full visibility, thus preventing damageof sensitive anatomical structures, such as nerves or blood vessels inthe surgical working area of the medical procedure.

The facial bone tissue of the maxilla may be located on the externalside of the maxilla adjacent to the alveolar ridge thereof.

Implanting the medical implant with the apical anchoring portion thereofmay comprise bringing the apical anchoring portion into bone appositionin the anchoring bore. The coronal end portion of the medical implantmay be brought into apposition to the bone tissue at the first recess.Thus, the first recess when implanted may support the medical implant.

As can be seen in the comparison shown in FIGS. 5A and 5B, a lever armmay be minimized and bending moments on the medical implant may beminimized, compared to conventional implants. The minimization ofbending moments is advantageous for long-term stability of theimplant-supported dental restoration. The aligned implant according tothe invention even allows for use of an aligned abutment.

The method may comprise marking a position of a bone entry site in theskull bone prior to creating the anchoring bore.

They may comprise positioning a non-threaded portion of the medicalimplant under a mucous membrane, prophylactically treating or preventingconditions such as catarrh or irritation of the mucous membrane.

Remaining teeth of the maxilla of the patient may be extracted prior tothe creating the first recess.

The method may comprise incising a gingiva of the maxilla at an alveolarcrest of the maxilla.

The method may comprise creating gingiva flaps interior and exterior ofan alveolar crest of the maxilla; expanding the exterior gingiva flapfrom the alveolar crest of the maxilla to a zygomatic bone of thepatient adjoining the maxilla.

The inner gingiva flap may be temporary sutured temporary together inorder to create a well visible surgical working area.

A substantially planar bone surface may be created at the alveolar crestof the maxilla by removing soft bone tissue for creating a bonefoundation. Thereby a good basis for affixing dental restoration isprovided.

Suturing the gingiva after the implanting concludes the medicalprocedure.

The medical implant applied in the medical procedure may be a medicalimplant according to embodiments described above.

In a specific embodiment, the method of implanting a medical implant ina patient comprises the following steps, wherein some of the steps maybe made in another order or omitted in other embodiments:

610: extracting remaining teeth of a maxilla of the patient;

620: incising a gingiva of the maxilla;

630: creating gingiva flaps interior and exterior of an alvolear crestof the maxilla;

640: expanding the exterior gingiva flap from the maxilla to an oszygomaticus of the patient adjoining the maxilla;

650: temporary suturing inner gingiva flap together to create a line ofsight;

660: removing still existing tooth fragments from the maxilla;

670: creating a substantially planar bone surface at the alveolar crestby removing soft bone tissue for creating a bone foundation;

680: marking a position of a drill hole entry in the os zygomaticus;

690: creating a recess in the maxilla external side that is aligned withthe position of the drill hole entry in the os zygomaticus; the recessis created in the exterior bone surface of the maxilla, which isoriented towards the facial side of the maxilla; the recess is made tohave a longitudinal extension oriented towards the zygomatic bone;

700: drilling a hole in the os zygomaticus from the position of thedrill hole entry in the os zygomaticus, aligned with the recess; therecess may be used as a guide channel for a drill when drilling a borein the zygomatic bone, whereby the recess in the outer surface of themaxilla is aligned with the bore in the zygomatic bone; the drillingoperation is performed under full visibility, thus avoiding damage ofsensitive anatomical structures such as nerves or blood vessels in thesurgical working area of the medical procedure;

710: implanting a medical implant with an apical part into boneapposition in the drill hole, and positioning a coronal part of themedical implant at the recess; the unthreaded portion of the medicalimplant is positioned under the mucous membrane, thus avoiding catarrhor irritation of the mucous membrane; the mucous membrane may at leastpartly embed a rough surface of the unthreaded portion of the medicalimplant; and

720: the medical procedure is finalized by suturing the gingivatogether, leaving the coronal end of the medical implant extendingthrough the gingiva for fixation of abutments or dental restorations.

The medical implant may for instance be of the type described above withreference to FIGS. 2 and 3.

In a method of creating a dental restoration, the method of implanting amedical implant in a patient as described above is applied. Consideringthe position in space of the connection interface of the implant at thecoronal end thereof, a dental restoration, such as a bridge is prepared.A plurality of medical implants may be provided in the patient.Subsequently the dental restoration is affixed to the connectioninterface of the at least one medical implant, at a coronal side thereofpositioned at a alveolar crest of the maxilla.

A further advantage of the above-described method is that the patientdoes not need to have clinically symptom-free sinuses. Pre-surgicalexamination is facilitated. A wider range of patients may be treated.

The present invention has been described above with reference tospecific embodiments. However, other embodiments than the abovedescribed are equally possible within the scope of the invention.Different method steps than those described above, different order ofthe method steps, etc. may be provided within the scope of theinvention. In addition, the different features and steps of theinvention may be combined in other combinations than those describedabove. The scope of the invention is only limited by the appended patentclaims.

1. An elongate zygoma implant for fixation in a patient, said implantcomprising an apical bone anchoring portion configured for apposition toa zygomatic bone of said patient, and a non-threaded coronal portion,wherein said coronal portion has a length (L₂) exceeding or equaling alength (L1) of said apical portion, wherein said apical portion has amaximum outer diameter (D1) that is equal to or larger than a maximumouter diameter (D2) of said coronal portion, and wherein the totallength of the apical bone anchoring portion and the non-threaded coronalportion is in a range of 30 mm to 55 mm.
 2. The implant according toclaim 1, wherein a ratio of a length of said apical portion (L1) to saidlength of said coronal portion (L2) is in a range of 0.2 to 0.5.
 3. Theimplant according to claim 2, wherein a ratio (D₁/D₂) of a said maximumouter diameter (D₁) to said maximum outer diameter (D₂) of said coronalportion is in a range of 0.5 to 0.95.
 4. The implant according to claim3, wherein said maximum outer diameter (D₂) of said coronal portion issmaller than a diameter of valleys of threads at said apical portion. 5.The implant according to claim 1, wherein said apical bone anchoringportion comprises a tapered top portion, wherein said tapered topportion is tapered towards an apical end of said implant and an apicalend diameter is less than half of said maximum outer diameter of saidapical portion (D₁).
 6. The implant according to claim 5, wherein saidtapered top portion is tapered with a tapering angle (α) in a rangebetween 25 to 75 degrees.
 7. The implant according to claim 1, whereinsaid coronal portion is rotationally asymmetrical.
 8. The implantaccording to claim 1, wherein said coronal portion is tapered towards acoronal end of said medical implant.
 9. The implant according to claim1, wherein a recess of a connection interface at a coronal end of saidimplant is substantially oriented in a longitudinal direction of saidmedical implant.
 10. The implant according to claim 1, wherein saidmedical implant is made of a monolithic single piece.
 11. The implantaccording to claim 1, wherein said apical bone anchoring portioncomprises a helical thread for said bone anchoring.
 12. (canceled) 13.The implant according to claim 1, wherein said coronal portion isconfigured for gingiva apposition.
 14. The implant according to claim 1any of the preceding claims, wherein said coronal portion is configuredfor partial radial apposition to bone tissue and partial radialapposition to non-bone tissue along a longitudinal portion of saidmedical implant. 15-28. (canceled)